ABSTRACT
BACKGROUND: In order to achieve a maintenance level and to prevent hemorrhagic complications, regular monitoring of the INR is mandatory for patients on oral anticoagulation therapy (OAT). A point-of-care instrument for INR monitoring is convenient for users, but the accuracy of the results has been controversial, and so this calls for exact evaluation of the point-of-care instrument that is used for INR monitoring. METHODS: From Aug 2007 through Feb 2008, 85 patients on OAT among the all the patients who were admitted to Soonchunhyang University Bucheon Hospital were involved in this study. Parallel measurements of the PT INR were performed using a CoaguChek-XS and, a CA-7000 laboratory reference instrument and the results were analyzed. In addition, the patients' clinical data, including the diagnosis and the frequency and interval of the INR measurements, were also analyzed. RESULTS: Of the 85 patients, 25 were admitted more than once to undergo INR testing and the mean interval between testing was 8.6 weeks with 39% and 38% of the tests being less than INR 2 units with using the CoaguChek-XS and the reference method, respectively. The coefficients of variation of CoaguChek-XS were 4.50 and 2.45 for the high and low INR patients, respectively. An excellent correlation was found between the two methods with a R2 of 0.966 (p<0.001). Through Bland-Altman analysis, the mean INR difference between the two methods was 0.13 with the limit of agreement being -0.47 +0.72 with a 95% confidence interval. CoaguChek-XS was shown to overestimate the INR value for patients with an increasing INR, as compared to the reference method. CONCLUSION: CoaguChek-XS demonstrated great precision and accuracy for patients on OAT when compared to the laboratory INR results. Accordingly, the instrument should help to monitor the INR in the patients on OAT.